Human and environmental risk ranking of onsite sewage disposal systems for Oahu

Abstract

This study evaluated the human health and environmental risk posed by on-site sewage disposal systems (OSDS). Oahu, Hawaii, was chosen as the study area for this project to develop and implement the methodology that will be applied to other islands in the future. The specific objectives of this study were to: • Estimate the quantity and types of OSDS on Oahu; • Estimate the effluent load discharged to the environment by these systems; • Identify which individual critical receptors (drinking water sources, streams and near shore waters) are most impacted by OSDS; • Identify other factors contributing to potential risk of OSDS; • Develop a risk scoring scheme based on various factors to assist regulatory managers in prioritizing inspection efforts for OSDS; and • Assign a risk score to each OSDS.